1. Field of the Invention
The invention relates in general to displays or signs, and more specifically to displays or signs which include a lens which is illuminated from the back side.
2. Description of the Prior Art
Certain public displays or signs include a lens assembly having a transparent legend or message plate and a transparent lens, which assembly is illuminated from the back by a lamp or other suitable source of light. The lens is normally held in position by a cover plate, which must be removed to gain access to the message plate and/or the lamp, for replacement thereof. This usually involves the removal of a plurality of screws, which is time consuming, and therefore costly. The screws, being viewable by the public, also invite vandalism. The relamping cost is especially high when a relatively large number of such signs are grouped, such as used as tenant signs in an elevator car, as each lamp burn-out necessitates a special service call to simply replace a lamp. If the replacement procedure is time consuming, it adds still further to the cost. The elevator car also presents a fairly severe service burden on a lamp, especially an incandescent lamp, because it is turned on and off in response to car position, and the constant starting and stopping of the car vibrates the lamp filament.
Thus, it would be desirable to simplify the relamping of illuminated displays, as well as the changing of message plates. It would also be desirable to eliminate visible screws or other fastening means which invite vandalism.